Kriya Yoga is mentioned in a number of Hindu scriptures, most often by referencing part of the technique. Specifically, the interested reader is referred to two Hindu texts: Patanjali's Sutras and the Bhagavad Gita.
These texts were originally composed in Sanskrit. In early days we did not have printing presses. Because of this, Sanskrit stanzas are highly compressed making it relatively easier to memorize or commit to parchment by hand. The compression together with the nature of the subject make it difficult to decipher the true meaning. However as a person deepens his or her meditation, true understanding slips out from inbetween the words and lines.
In addition to religious scripture, we also have mythology. Mythological tales are an easier, but less precise way for societies to preserve and communicate spiritual knowledge. Some dismiss it as fantasy. But often historical events are interwoven with spiritual truths. For example in the epic Mahabharata, the blind king Dhritarashtra represents the blind mind. Our mind is constantly preoccupied with data feeds from the five senses and it's own machinations. It is therefore blind to the nature of true existence, hence the "blind king/mind". Thus the mythological tale of the Mahabharata is symbolic of our internal Mahabharata.
Each sentient self-aware being carries within it the complete blueprint for spirituality. All that is required is the right practice and the urge/will/discipline to practice. In this sense, Kriya is as old as the very first breath, regardless of the vehicle of that first breath.
Beyond India and Hindu scripts, there are symbolic references in all the major traditions, in paintings, descriptions, sculpture and religious practice. During learning and practice we do not refer to these however. First of all there are too many and secondly, students of Kriya discover these for themselves as they progress in their practice. These intermediate "aha" moments are necessary validation that they are on the right track, but they are not necessary for learning and practice. Were they to be described, then the future "aha" moment could be contaminated by doubts - "did I make this connection because I read about it? or did I imagine it?".
In the last couple of hundred years, the teaching of Kriya Yoga Meditation has been revitalized and made available outside India through the efforts of realized Yogi's Babaji, Lahiri Mahasaya, Sri Yukteswar and Paramahansa Yogananda.
Sadly, Kriya has also become commercialized with many claiming to teach the "genuine" article. As my son would say, "Go figure...!"
I met Swamiji in 1987. Only when he taught me the technique did I realize that I had already been practicing the Hong Sa form of meditation for over a decade.
For almost 30 years he guided me on my journey. In 2016, I formally left his organisation in order to concentrate on my own spiritual practice and advancement; rather than pushing, I am now pulled by my inner self/prana. I have been fortunate to have helped him co-author "Kriya Yoga Darshan", a 250 page book on spirituality and Kriya Yoga meditation.
I teach and guide students in the same way that he received it from his masters and based on my own direct experience, as opposed to just theoretical understanding.